.\" Copyright 1998 Andries E. Brouwer (aeb@cwi.nl)
.\" Copyright 2007 Karel Zak <kzak@redhat.com>
.\"
.\" May be distributed under the GNU General Public License
.TH BLOCKDEV 8 "August 2010" "util-linux" "System Administration"
.SH NAME
blockdev \- call block device ioctls from the command line
.SH SYNOPSIS
.B blockdev
.RB [ \-q ]
.RB [ \-v ]
.I command
.RI [ command \&...\&]
.I device
.RI [ device \&...\&]
.br
.B blockdev
.B \-\-report
.RI [ device \&...\&]
.br
.B blockdev
.BR \-h | \-V
.SH DESCRIPTION
The utility
.B blockdev
allows one to call block device ioctls from the command line.
.SH OPTIONS
.IP "\fB\-q\fP"
Be quiet.
.IP "\fB\-v\fP"
Be verbose.
.IP "\fB\-\-report\fP"
Print a report for the specified device. It is possible to give multiple
devices. If none is given, all devices which appear in
.I /proc/partitions
are
shown. Note that the partition StartSec is in 512-byte sectors.
.IP "\fB\-h\fR, \fB\-\-help\fR"
Display help text and exit.
.IP "\fB\-V\fR, \fB\-\-version\fR"
Print version and exit.
.SH COMMANDS
It is possible to give multiple devices and multiple commands.
.IP "\fB\-\-flushbufs\fP"
Flush buffers.
.IP "\fB\-\-getalignoff\fP"
Get alignment offset.
.IP "\fB\-\-getbsz\fP"
Print the blocksize in bytes.
This size does not describe device topology.  It's
the size used internally by the kernel and it may be modified (for example) by
filesystem driver on mount.
.IP "\fB\-\-getdiscardzeroes\fP"
Get discard zeroes support status.
.IP "\fB\-\-getfra\fP"
Get filesystem readahead in 512-byte sectors.
.IP "\fB\-\-getiomin\fP"
Get minimum I/O size.
.IP "\fB\-\-getioopt\fP"
Get optimal I/O size.
.IP "\fB\-\-getmaxsect\fP"
Get max sectors per request
.IP "\fB\-\-getpbsz\fP"
Get physical block (sector) size.
.IP "\fB\-\-getra\fP"
Print readahead (in 512-byte sectors).
.IP "\fB\-\-getro\fP"
Get read-only. Print 1 if the device is read-only, 0 otherwise.
.IP "\fB\-\-getsize64\fP"
Print device size in bytes.
.IP "\fB\-\-getsize\fP"
Print device size (32-bit!) in sectors. Deprecated in favor of the
.B \-\-getsz
option.
.IP "\fB\-\-getss\fP"
Print logical sector size in bytes \(en usually 512.
.IP "\fB\-\-getsz\fP"
Get size in 512-byte sectors.
.IP "\fB\-\-rereadpt\fP"
Reread partition table
.IP "\fB\-\-setbsz\fP \fIbytes\fP"
Set blocksize. Note that the block size is specific to the current file
descriptor opening the block device, so the change of block size only persists
for as long as
.B blockdev
has the device open, and is lost once
.B blockdev
exits.
.IP "\fB\-\-setfra\fP \fIsectors\fP"
Set filesystem readahead (same as
.B \-\-setra
on 2.6 kernels).
.IP "\fB\-\-setra\fP \fIsectors\fP"
Set readahead (in 512-byte sectors).
.IP "\fB\-\-setro\fP"
Set read-only. The currently active access to the device may not be affected by the change. For example,
a filesystem already mounted in read-write mode will not be affected.
The change applies after remount.
.IP "\fB\-\-setrw\fP"
Set read-write.
.SH AUTHORS
blockdev was written by Andries E.\& Brouwer and rewritten by Karel Zak.
.SH AVAILABILITY
The blockdev command is part of the util-linux package and is available from
https://www.kernel.org/pub/linux/utils/util-linux/.
